chore: port backend optimize_pages changes

[hardy-dev-infinilabs]

Summary

• port the backend-side optimize_pages changes on top of the shared build and package pinning base
• include setup, security, agent/gateway install, elastic API, and managed-server backend updates from the source branch
• keep the build and generated-file workflow changes isolated in console#339 so this PR focuses on backend behavior

Dependencies

• console#339

[hardy-dev-infinilabs]

Closing this large port PR in favor of smaller scoped replacements. I will follow up with split PRs for security/token, managed agent credential flow, and other focused changes.

[hardy-dev-infinilabs]

Superseded by smaller PRs: #342, #343, #344, and #345.